Fast DownLoad lets clients download files at HTTP speed through the internet, instead of the game. It goes much faster for almost any file, and BZ2 zipping the file makes it go even faster.
This worked for me, I just named it "source" instead of "garrysmod"
Setup FastDL:
http://www.facepunch.com/showthread.php?t=899166
BZ2 Zipping Program
http://www.killercreation.co.uk/forums/ ... ttach_id=7
To use the BZ2 zipper, drag a file over the icon and drop it. It will zip the file and place it in the folder.
Hope it helped.